In materials handling vehicles, it is often desired to vary the amount of braking force applied according to certain factors. Hydraulic brakes provide for great flexibility in the amount of braking force applied, but hydraulic brake systems are expensive because of the required space for hardware and plumbing. Electric brakes are frequently used in materials handling vehicles, particularly electrically powered vehicles, because of their size and simplicity; however, electric brakes normally do not lend themselves to being variable in the braking force applied. Usually, they are either on or off.
In certain vehicles, it is desirable for the braking force to be varied to some extent to accommodate the configuration of the vehicle. For example, when the vehicle is moving with its load raised or when the vehicle is in a tight turn, heavy braking should be avoided. Under these circumstances, equipping the vehicle with an electric brake that applies less than full braking force would be desirable.